-təs noun
( plural rictus or rictuses )
Etymology: New Latin, from Latin, open mouth, from rictus, past participle of ringi to open the mouth, show the teeth; akin to Old Slavic ręgnǫti to gape, and perhaps to Old English wrencan to twist — more at wrench
1. : the gape of the mouth of a bird
2.
a. : the mouth orifice
b. : a gaping or grimace
a face frozen in a rictus of terror